General idea of the scintillation-counter lay-out for the SC experiment on the scattering of polarized protons

This photograph gives a general idea of the scintillation-counter lay-out for the SC experiment on the scattering of polarized protons reported on p. 116. The polarized-proton target is hidden by its magnet (marked PT 1) ; incident protons reach the target through apertures in the concrete shielding (foreground) and the magnet yoke. Protons scattered to the right at any one of eight chosen angles are detected by means of coincidences between the signals from the corresponding pair (one behind the other) of plastic scintillation counters, clearly visible ; absorbers between some of the pairs are for energy measurements. To the left of the target can be seen a long plastic scintillation counter, with two photomultipliers, of the type mentioned by Prof. Cocconi in last month's CERN COURIER (p. 105). Protons recoiling from the target travel in this direction and the position of each one as it strikes the counter is measured, thus defining its direction of travel. In this way each scattered proton can be associated with its corresponding recoil proton, separated from the general background. Other counters in the background are used in lining up the beam. G. Goignet is adjusting the counter on the left and J. Monmejat is at the back.